Implement function that drops privileges by:

Implement function that drops privileges by:
- chrooting to /var/empty (user hast home directory),
- setting groups to 'hast' (user hast primary group),
- setting real group id, effective group id and saved group id to 'hast',
- setting real user id, effective user id and saved user id to 'hast'.
At the end verify that those operations where successfull.

MFC after:	1 week